Angle-measuring instrument.



PATENTED PEB. 6, 1906.

A. KNIG. ANGLE MEASURING INSTRUMENT.

APPLOATION FILED DEG.Z2,1904.

2 SHEETS-SHEET 1.

No. 811,777. PATENTED FEB. 6, 1906. A. KNIG.

ANGLE MEASURING INSTRUMENT.

APPLICATION FILED DBO. 22, 1904. 2 ISHEETS SHEBT 2.

Wwf/Wyse 5' UNITED STATES PATENT FFICE.

ALBERT KNIG, OF JENA, GERMANY, ASSIGNOR TO THE FIRM 0F CARL ZEISS, 0F JENA, GERMANY ANGLE-MEASURING lNSTHUMENT.

.To a/ZZ whom` t may concern:

Be it known that I, ALBERT KNIG, doctor of philosophy, a citizen of the German Em pire, residing at Carl-Zeiss-Strasse, Jena, in the Grand Duchy of Saxe Weimar, German Empire, have invented a new and useful Angle-Measuring Instrument, of which the following is a specification.

The invention relates to free-hand instruments in which with a telescope a device is combined for measuring the angular distance of the point observed through the telescope in relation to the invariable direction of a terrestrial force either gravity or the horizontal component of terrestrial magnetism. Instruments of this kind are provided with a body hereinafter called a director, which is rotatable on an axis fixed to the telescope and stands under the iniiuence of the terrestrial force, so that the telescope may be rotated in a plane perpendicular to the axis of the director'without a change in the position of the director relatively to the direction of the terrestrial force. For determining the angular position of the telescope relatively to the direction of the terrestrialforce a circular scale is fixed to the director concentrically to the axis of rotation, the index being rigidly connected with the telescope. This class of instruments embraces such telescopic instru` ments for measuring angular altitudes and other vertical angles in which a pendulum serves as the director and such telescopic or bearing-Compasses and other instruments measuring horizontal angles in which a magnetic needle is the director.

The free-hand instruments of this descrip tion are modified according to the invention in such a way that the observer is enabled to read oli' the angular distance in the telescope itself. In order to attain this object, the cylindrical scale connected with the director is made to pass through the eld of .view of the telescope, preferably touching the focal lane of it in a straight line passing throng i the focal point.

In order to render the division of the scale sharply visible even toward the margin of the field, the radius of curvature of the scale may be enlar ed by deviating from the cylindrical form. For instance, the simplest form, the plane one, may be adopted for the scale, which is then entirely transferred into the focal plane; but in these cases the telescope Specification of Letters Patent. Application filed December 2li. 1904. Serial No. 238,008.

Patented Feb. 6, 1906.

must be a broken one in the articular case of the plane scale a right-ang ed or a parallei-vision telesco e. In all cases of broken telescopes the de ecting-prisms may be so arranged that they act in addition to breaking the optical axis as a means for rerecting the image. Examples of such arrangement are the prism systems of the prismatic fieldglasses. y

A further advantage in the free-hand use of these instruments improved as described is obtained b such a relation between the focal lengtho the objective and the diameter of the scale that the angular values of the image produced in the focal plane are equal to those of the scale. This is the case whenever the focal length of the ob'ective is equal to the radius of the scale. If in that event the direction of the telescope in the plane of rotation of the scale be altered, the scale and the telescopic image will pass over the field of view Without any appreciable change in their relative position. With instruments of this construction an index-Wire in the image-field of the telescope can be dispensed with, as no longer is only one line of sight available, but accurate readings are possible in any position Within the field of the image-point under observation.

In the accompanying drawings, Figure 1 is a horizontal section through a bearing-compass. Fig. l is a longitudinal vertical section through the same compass. Fig. 2 is a longitudinal vertical section through an instrument for measuring angular altitudes, ositive as Well as negative. Fig. 2a is a ront view of the same instrument, the occular being removed. Fig. 3 is a longitudinal vertical section through another bearingeornpass. Fig. 3 is a plan view of the same compass. Fig. 4 is a horizontal section through another altitude instrument. Fig. 4a is a longitudinal vertical section through the same instrument. Fig'. 5 is a transverse vertical section through a third bearing-compass. Fig. 5a is a plan view of the same compass. Fig. 6 is alongitudinalvertical section through a fourth bearing-compass. Fig. 6a is a plan view of the same compass.

The bearing-compass' shown in Figs. 1 and l comprises `an astronomical telescope'composed of the objective O and the eyepiece o and the compass-needle m, (the director,) rotatable on the fixed axle A and carrying the IOSV cylindrical scale s coaxially. This scale is made of lass or some other transparent material an its axis being the a 's of rotation of the needle intersects the o tical axis of the telescope at right angles. he scale touches the focal lane of the telescope in proximity to the index-wirei and re asses,w1th its oppoint, the ield so o osely to the objective O that this second passage is not perceived by the observer. The operation is as follows: The compass is taken in the free hand and directed toward the object until the teleposite sco ic image of the latter is seen to be cov-y ere by the index fi. Then that point of the slightly oscillating scale is read oi, the amplitudes of which right and left of the wire are equal. The scale is adjusted to the compass-needle in such a Way thatthe angle read off is that between the direction to the object and the magnetic meridian.

In the angular altitude instrument represented in Figs. 2 and 2 the pendulum p (the director) carries the cylindrical scale s, which differs jfrom that in Figs. land 1a in so far as it extends merely through a quadrant. The operation is essentially the same as with the instrument shown in Figs. 1 and 1a.

In Figs. 3 and 38a bearin -compass is shown in which the cylindrica scale is replaced by an ordinary (but transparent) plane graduated compass-card `s. he eyepiece o stands vertical, and a reflecting-prism a is situated below the focal plane in which the scale 3 rotates. This Well-known.` prism erects the inverted telescopic image not only in respect of to and bottom, but also laterally, owing to the slanting position of its refleeting surfaces which form a ridge. The instrument is thus provided with a right-angled terrestrial telescope. The compass shown in Figs. 3 and 3a is also an example of the arrangement above dealt with-viz., that the focal length of the objective is equal to the radius of the scale. In consequence thereof the indexhas been omitted. j

The altitude instrument, Figs. 4 and'4, is likewise iitted with a plane scale 8, and also with an index if. The telesco e is a parallel vision terrestrial telesco e. he irst of its prisms, a double-reflecting Prandl rism b,

. produces no change in the position o the telescopic image, while the rism a, thesame as in Figs. 3 and 3", erects t `s image.

The bearing-compass shown in Figs. 5 and of the telescope 5 and that shown in Figs. 6 and 65 are also each provided with a parallel vision terrestrial telescope.` In both examples aplane compass-card s", as in Figs. 3 and 3, is employed, but in Figs. 5, and 5 the direction ofl the line of sight of the telescope is tangential to the card and in Figs. 6 and 6il diametrical, while owing to the different arrangement of the prisms the observer will see the division of the scale upright in both cases. The rism system in Figs. 5 and 5a, consisting o four totally-reflecting risms I, II, III, and IV, is the less usual of the two Porro reversing systems. In Fi s. 6 and 6a the same four prisms are arrange in the order of the other Porro system well known from the prism fieldglasses.

What I claim ,as my invention, and desire to secure by Letters Patent, is-

1. A telescopic angle-measuring free-hand instrument consisting of a telescope, a circular scale rotatable about an axis-which is central to it and xed relatively to the telescope-and passing through the focus ofthe telescope transversely to the optical axis, and a director rigidly connected to the scale and subject to an invariable terrestrial force.

2. A telescopic angle-measuring Jree-hand instrument consisting of a telescope, a transparent circular scale rotatable about-an axiswhich is central to it and fixed relatively to the telescopeand passing through the focus of the telescope transversely to the optical axis, and a director rigidly connected to the scale and subject to an invariable terrestrial force.

3. A telescopic angle-measuring free-hand instrument consisting of a telescope, a transparent circular scale rotatable about an axiswhich is central to it and fixed relatively to the telescopeand passing through the focus transversely to the optical axis, and a director rigidly connected to the scale and subject to an invariable terrestrial force, the focal lgth of the telescopic objective being equal to the radius of the scale.

In .testimony whereof I have signed my name to this specification in the presence of two subscribing witnesses.

ALBERT KNIG.

Witnesses PAUL KRGER, FRITZ SANDER.

IOO 

